1. Field of the Invention
The present invention relates to a method of manufacturing a mesoporous alumina molecular sieve and an alumina nanotube by using a surfactant and a use of the alumina nanotube as a hydrogen storage material.
2. Description of the Related Art
Generally, alumina is considered an important catalyst and support in industrial processes. A reaction of mesoporous alumina with uniform porosity, high surface area, chemical stability and thermal stability is becoming more valuable than existing alumina with non-uniform pore distribution.
Various surfactants, such as cationic, anionic, neutral and nonionic surfactants have been used in producing alumina with mesopores. Specifically, there have been reports in producing alumina with mesopores and high surface area, by using a nonionic surfactant, a sodium dodecyl sulfate and a long chain carboxylic acid.
However, due to an extremely rapid hydrolysis of alumina in an aqueous solution, it is difficult to synthesize mesoporous alumina molecular sieve using a cationic surfactant. Even in the presence of a surfactant, a hydrated hydroxide in a lamellar form can be produced. Therefore, additives such as triethanoleamine, a hydrolysis inhibitor, are added to prevent rapid hydrolysis in synthesizing mesoporous alumina molecular sieve. Currently, a method of producing mesoporous alumina molecular sieve with high surface area, good thermal stability and simple production method is in demand.
Hitherto, there have been reports on methods of producing mesoporous alumina materials with pore structures of a wormhole or sponge-like motifs by utilizing a supramolecular assembly phenomenon of a surfactant, but there are no reports on producing alumina nanotube by using surfactants.
There have been reports on the reaction of alumina fiber in a nano-structure, by sol-gel process, in which temperature is continuously raised until a predetermined cut-off temperature. There have also been reports on the reaction of alumina nanotube by an electrochemical anodizing method. However, these processes cannot produce a large amount of alumina nanotube.
There has been no report regarding the usage of an alumina nanotube as a hydrogen storage material.
Hydrogen is considered an infinite energy source since hydrogen can be obtained from the earth's water source and it can be recycled back into water form after combustion. Hydrogen is a clean energy source since it produces only water, and not environmental pollutants during combustion. Hydrogen energy can be used in almost all industries, including transportation and electricity generating systems. However, a problem in using the hydrogen energy has been raised due to lack of developments on simple and economical hydrogen storage system.
Hydrogen can be physically stored in a high-pressure chamber by compressing the hydrogen beyond 100 atm. But loading the chamber on a transportational vehicle is extremely dangerous. Also, another physical storage method involves storing the hydrogen at an extremely low temperature, below its boiling point (20.3K). However, although this method allows storing large amount of hydrogen by reducing the storage volume, the cost of equipments used in maintaining the low temperature is too high.
Hydrogen can be chemically stored by using a hydrogen storage alloy. Although such method efficiently stores hydrogen, with repeated cycle of storage and release of hydrogen, impurities may enter and cause deformation of the hydrogen storage alloy, which leads to a deterioration of the hydrogen storage capacity. Also, because a metallic alloy is used as the storage medium, the weight per unit volume increases, thus, it is difficult to load the storage alloy onto a transportation instrument.
Another hydrogen storage method is achieved by forcing adsorption of hydrogen gas on to a solid material. Among such methods, hydrogen storage by carbon nanotube or nano-structured carbon materials shows hydrogen storage efficiency exceeding 10 wt. %. However, these results are difficult to reproduce and many researches are continuing to overcome problems caused by such method.
There are ongoing active researches to develop a hydrogen storage method that reaches at least 6.5 percent by weight of storage efficiency, which is the target hydrogen storage required by the US Department of Energy (DOE), while providing stability and economical efficiency.